Wasatch Weather Weenies

It's been a while since we've had an airmass push into Utah from the northwest, but it happened last night and it brought the smoke from a distant fire, partially obscuring the Wasatch Mountains this morning. The smoke is from fires in Oregon and possibly northern California. Source: NIFC The 2-day loop below shows the push of high pressure and northwesterly flow into Utah overnight.   And with the smoke came a bump in PM2.5 concentrations overnight, as if we don't get enough crappy air in the winter. Source: Utah DAQ It will be nice when those fires are out and the northwest returns to a source of pristine air!

Thanks to an active series of monsoon surges the Wasatch are remarkably lush right now, with firm, moist trails (at least on north aspects) and a jungle-like feel (by Utah standards). Adding to the ambiance was a light, steady shower in the early afternoon.  That shower was produced by an approaching upper-level trough in the westerly midlatitude flow – a harbinger of the return of the storm track as fall approaches (hooray!). Indeed signs of fall are beginning to appear, with a few trees already beginning to pack it in, even at these lower (7000–8000 ft) elevations. Boy scouts are working to realign the trail in the area we were in today.  Although it's great they are out working on the trails, we wondered why the realignment was needed and the existing trail was in pretty good shape.  All we could figure was that there's a desire to move the trail away from the stream that runs down the canyon.  However, it appeared this was being done at the expe...

Living a long life typically requires hitting the genetic jackpot, living in a relatively safe and healthy environment, taking care of yourself, and then perhaps just being plain lucky.   Swiss mountain guide Ulrich Inderbinen provides such an example .  He climbed the Materhorn 390 times, summited it a final time when he was 90, climbed 13,000 foot peaks in his 90s, worked until he was 95, and passed away this summer at 103.  Not too shabby. Although not as far out there on the longevity limb as Ulrich Inderbinen, "Tropical" cyclone Cristobal, which moved poleward off the west  east coast of North America this week, lived a pretty good life, benefiting from a caterpillar-to-butterfly-like metamorphosis from a tropical cyclone into a midlatitude cyclone as it moved into the North Atlantic.   At the beginning of the loop below, Cristobal is barely a glint in his parent's eye and just a weak cluster of thunderstorms associated with a tropical easterly wave...

There is a nice article in the latest EOS , a publication of the American Geophysical Union, discussing the remarkable ice cover on the upper Great Lakes this past spring [See Cold Water and High Ice Cover on the Great Lakes in Spring 2014 by Clites et al. (2014), unfortunately paywalled unless you are an AGU member and login with your membership account]. Source: Clites et al. (2014) Some tidbits from the paper: Lake Superior wasn't completely ice free until  June 6th.   Yeah, June! At the end of April, 51% of Lake Superior, 23% of Lake Huron, and 10% of Lake Michigan were still ice covered.  In the 40-year period of record at the end of April, the previous record on Lake Superior was 30%, in only a few years was significant ice observed on Lake Huron, and at no time was their significant ice on Lake Michigan. A quick look at data from NCDC shows that this past Dec–Apr was the coldest in Michigan (which flanks Lakes Superior, Michigan and Huron) since 192...

What an August it has been.  Lots of rain and relatively cool days.  Nobody can complain this year. Although it has been wet, a quick look at the weather records suggests that the area has seen wetter.  Let's start with the Salt Lake City International Airport.  Through yesterday, the accumulation for August 1–27 was 1.77 inches (green line), well above average (brown line).  That ties it for 8th amongst the wettest August 1–27 periods.  However, there have been similar periods in past years that were much wetter, including 1968 when 3.66 inches fell (blue line). Source: NWS Given the fickle nature of monsoon convection, however, observations at a point can sometimes be misleading.  Let's look at a few other stations. Alta has been deluged this August with an accumulation of 5.33" so far, which puts it just behind 1983 (5.97").  There is some missing data for the period though (black dots), including yesterday, which will add to the tota...

Where is the coldest air in the continental United States?  Well, if we go up to 500 mb, which sits about 18,000 feet above sea level at an area where the presence of cold air is frequently associated with thunderstorm formation, it's over northern Utah and eastern Nevada, with a close 2nd for the upper Dakotas (technically the analysis below is a 6-hour forecast, but let's call it good). GFS Forecast 500-mb temperature at 1800 UTC 26 Aug 2014 Accompanying that pocket of cold air is a weak 500-mb trough centered over Nevada. With the pocket of cold air, monsoon moisture, and surface heating, thunderstorms are likely across much of Utah this afternoon and are even possible overnight thanks to the dynamical forcing of the upper-level trough (you may have heard some last night).  When it comes to storms like these, however, their development and evolution occurs over periods of at most a couple of hours.  Therefore, forecasting the where and when is pretty much im...

Today is the first day of Fall Semester at the University of Utah.  Welcome to all the students, new and continuing.  Even those on double secret probation (you know who you are). If you are new to Utah, consider yourself fortunate.  We have had a remarkably cool and wet August, especially over the past several days.  Average high temperatures for the month so far are 3.3ºF below average, and we've had 1.57" of rain at the Salt Lake City Airport compared with an average of 0.69".  It's been especially cool the past several days when many of you have arrived, moved into your dorms or apartments, and told the parents adios.  Over the past two days, we haven't even hit 80ºF! Source: NWS If you are coming from out of state, this weather is isn't normal.  The average high for today is 88ºF, with a record of 100ºF.  When you look for a new place for the next academic year, don't just find good roommates, find an air conditioned unit too.

Source: http://meso1.chpc.utah.edu/station_cameras/armstrong_cam/armstrong_cam_hour.mov

Source: NWS If you search hard enough in the forecast grids for the Wasatch Mountains this morning, you can find a few locations with a predicted rain/snow mix for tomorrow (see above).   The cause is an approaching mid-latitude trough that will be over northern Utah tomorrow.   Temperatures on Saturday are low enough that snow levels in the GFS drop to as low as 10,500 feet. This is also a situation in which heavy precipitation can develop, which often results in a temporary lowering of the snow level.  Further, the gold-standard ECMWF model is even cooler than the GFS, so don't be surprised if you see flakes on the high peaks this weekend.

It's been a great month for plants in northern Utah and the unsettled weather will likely continue through Saturday. For all intensive purposes, our wet weather began in late July.  Since July 28th, measurable precipitation totaling 1.47 inches has been recored on 10 days, with trace amounts on 3 additional days.  That's about double the climatological average for the period (around 0.77 inches). Over the past 30 days, precipitation across most of northwest Utah is now running 150% or more above average and in some instances more than 300% of average. Source: NWS More rain is coming.  In addition to the unsettled monsoon weather, a broad mid-latitude trough is moving into the area and is expected to interact with the monsoon moisture and further stimulate precipitation late Friday and Saturday. So, we should have a very impressive precipitation anomaly relative to average for the 30-day period ending Saturday.  What a great summer! 

The American Meteorological Society Mountain Meteorology Conference is in San Diego this week.  Early in the week, it was an extremely difficult assignment to sit in a dark conference room and suffer death by powerpoint when it looked like this outside. In general, interesting weather avoids meteorologists like the plague and you'd figure that that would be especially true in San Diego which probably has the most benign weather in the U.S.  In August, in particular, the average rainfall is only 0.06".  Today, however, we we treated to a glimpse of a rare beast: The California Thunderstorm. It didn't look like much on radar, but those are some fairly high returns exceeding 50 dBZ just offshore. Source: NCAR/RAL Lightning?  Yeah, plenty of strikes, primarily offshore. Source: http://www.lightningmaps.org/ Most of the locals just continued their outdoor recreation, but with thunder and lightning in the area, I headed in quickly from my morning w...

A few days ago I announced the arrival of a monsoon break and suggested that it would likely remain dry for several days (see Arrival of the Monsoon Break ).  Well, we got a few days of dry weather, but a monsoon surge snuck into Utah last night and rain is falling this morning across northern Utah. Source: NCAR/RAL This forecast bust provides a nice example of how subtle changes in the large scale forecast can bite you in the rear during the monsoon.  The GFS forecast from 6Z last Friday called for an elongated upper level trough to extend from the eastern Pacific into northern California, placing Utah in a relatively dry southwest to westerly flow aloft. Instead, the trough verified along the California coast, placing Utah in southerly to southwesterly flow that tapped into moisture from the monsoon region.  Really, this was a full blown forecast bust for all of the southwest U.S. it is also far wetter in Arizona than forecast a few days ago. The surge o...

Eighteen years in Salt Lake City and I've never hiked up Clayton Peak, which lies above Brighton in upper Big Cottonwood Canyon. I did it today and discovered that there might be no better place to sit and think about how the topography influences the snow climate of the Wasatch Mountains. The image below, in particular, was taken to highlight the high terrain surrounding Little Cottonwood Canyon (LCC, click to enlarge).  Mt. Timpanogos to the south is higher than any of the topography surrounding LCC by a couple hundred feet, but it is an elongated ridge.  As a result, it sees heavy snowfall primarily when the flow crosses that ridge (i.e., out of the south or southwest), but not so much in other patterns.  The island of topography surrounding LCC, however, while famous for snowfall enhancement in northwesterly flow, usually helps out some during storms featuring a wide variety of flow directions.  The great diversity of storms that can affect the high terrain s...

For some reason, I've always been fascinated with the climate record for July.  Perhaps it's because it is the hottest month of the year at most (but not all) locations.  This year was particularly interesting. Let's start in Utah.  As we've discussed previously (see Near or Above Average Temperatures Are an Easy Bet in July ), you can usually count on above average temperatures in July in Utah, and this year didn't disappoint.  On a statewide basis, the average temperature was 75.5ºF, 3.0ºF above average and the 7th warmest July on record.  The last July with a statewide mean temperature below the 20th century average was 1997.   Source: NCDC At the Salt Lake city International Airport, we only had two days with a temperature above 100ºF (July 14 and 23rd, both of which hit 103ºF), and we had a really nice cool down during a big monsoon surge at the end of the month (high temperatures of 76, 82, and 85ºF on July 29, 30, and 31, respectively). Ne...

Mostly sunny skies over the Salt Lake Valley are a harbinger of things to come Change is underway over northern Utah as drier air gradually moves into the region.  Integrated precipitable water values, which indicate the total water vapor in the atmosphere, have been declining the past two days and have dropped to below 2 cm as drier air moves in. Source: ESRL Yesterday, we still had a few showers and thunderstorms around (congrats to you Utah County and other area residents who enjoyed a late-night splurge), but they should be widespread today and more confined to areas of high terrain.  Further, the models show relatively dry air in place over the next few days.  The time-height section below is based on forecast profiles of relative humidity (color fill) over the Salt Lake City for the next 180 hours (time increases to the left).  For the most part, it's fairly dry. Waxes and wanes in monsoon moisture and precipitation are known as monsoon surges and b...

My personal weed patch (a.k.a. lawn) is looking unusually lush for mid August with just a few patches of brown to be found.   It's a real pity that invasive annual grasses have taken over the landscape in the foothills or it might be a bit greener around town.   Here's an interesting plot for you from the National Weather Service that shows the departure from average precipitation over the past 14 days.  Northeast Nevada has had a "climatological deluge" with 600+% of average precipitation.  What I find interesting is that northern Utah and the northern Wasatch Front have also been fairly wet, with anywhere from about 110–600+% of average, but if this analysis is to be believed, portions of the Sevier Desert to our south have been remarkably dry.  Although such spatial variability is not unusual during the monsoon, in this case it could reflect a lack of radar coverage and gauge data in the area, so perhaps someone out there could dig into what gauges...

As the sun sets in the sky, its color often transitions from yellow to orange or even red.  Why? Sunlight is comprised of visible light of all colors and wavelengths.  Superman really didn't get his powers from the "yellow sun" because the sun isn't yellow, it's white. Source: http://www.stellarplanet.co.uk/ The white color reflects the fact that sunlight is comprised of light across the entire visible spectrum, which we can break down using the Roy G. Biv acronym where R=Red, O=Orange, Y=Yellow, G=Green, B=Blue, I=Indigo, and V=Violet.  This also orders the color by decreasing wavelength, with red having the longest wavelength and violet the shortest. As sunlight passes through the atmosphere, the shorter waves are scattered more easily than the longer waves.  This has two important effects.  First, it shifts the color of the sun from white toward the longwave or "ROY" part of the spectrum.  Second, it shifts the color of the sky, which deri...